Transparent conductive coatings are of great significance and are well known among other things for displays (e.g., CRT, LCD, and OLED) and/or antistatic coatings. Standard methods for manufacturing comprise among others first the gas phase coating (e.g., sputtering, CVD, PVC) of flat glass with thin, conductive coatings that are transparent in the visible world. Metals (e.g., precious metals), conducting or semi-conducting doped oxides such as ATO (SnO2:SB), FTO (SnO2:Sb), FFO (SnO2F), AZO (ZnO:A1) or ITO (In2O3:Sn) are used as coating materials. As a rule thick coatings are obtained via these methods. This is known as the standard method for coating flat glass in order to generate high-quality coatings.
The sputter facilities that are used for glass coating are quite expensive (2 to 3-figure million amounts) and work profitably only in the case of large operational capacity (coating of several 100 T m2/a). In addition, such facilities require high material consumption; because when either the material that is to be deposited or a target are vaporized, the vaporized material is only partially deposited on the substrate to be coated, while the rest settles somewhere in the interior of the machine. Further, such facilities are inflexible, such that small or special runs are impractical since only flat geometries can be coated using sputter facilities. Other geometries are only possible to a limited extent and the corresponding facility must be rebuilt with each change of geometry. This is somewhat of a problem for automobile glazing, because there are no absolutely flat automobile panes. Sputtering flat panes and then bending them has not succeeded up to this point. Even coating of polymers and films is only possible to a limited extent.
There have also been approaches for realizing such coatings via using conductive nanoparticies (e.g. ITO). Such methods exhibit advantages as a simple coating technique (e.g. via wet-chemical methods such as painting, spraying, pressing, dipping, and spin-coating), thereby permitting: (i) the direct application of coatings onto structures, (ii) a low technical expense with correspondingly low investment costs as a consequence, (iii) are geometry independent, (iv) make better use of the material, (v) have greater flexibility, and (vi) permit a coating of polymers and films.
One basic requirement is the availability of, for example, IT nanopowder suitable particle size and the redispersibility with the corresponding properties. It is known from U.S. Pat. No. 5,518,810 (Mitsubishi) that a specific shade of color correlates with optimum properties (e.g., infrared shielding). Typically blue is an indication of a high number of oxygen defects, thus a high charge carrier density, which is caused by oxygen defects. This is, as a rule, generated in ITO by annealing the powder or coatings of the powder under inert gas or reducing atmosphere, Specifically in the case of temperatures above 250° C., process results in blue powder having a higher conductivity than yellow powder that has not been retreated under reducing atmosphere, and this process results in coatings that have been reduced (e.g., by heat treatment at 500° C. in the air after inert gas/reducing treatment at temperatures above 250° C. show significantly higher conductivities). A subsequent temperature treatment of ITO coatings under reducing/inert atmosphere at temperatures above 250° C. is state of the art. However, with many technical applications such a subsequent treatment is often not desirable or not possible, since the coated objects are destroyed at the required temperature (e.g., with CRT or conductive and/or antistatic coatings on plastic). At the same time, however, the requirements and the need for highly conductive, transparent coatings on plastic are also increasing.
The object of the present invention relates to making something new available for industrial application.
The solution of this task will be claimed in independent form.